The present invention relates to a protective sheet material for use both above ground and below ground as well as to a method of making the material, and in particular, to a protective sheet material of a laminate structure having plastic and petroleum wax saturated felt layers.
Various structures, above ground and underground, require protection from corrosion resulting from a variety of causes. For example, underground metal structures such as pipelines require extensive protection from corrosion caused by moisture, chemicals and bacteria commonly found in soils. Various methods of protecting underground pipelines are used. One method is to wrap the pipeline with a wax tape composed of a synthetic fabric material, such as felt, saturated with a blend of petroleum wax, plasticizers and corrosion inhibitors. While wax tapes of this type provide the desired protection, in certain soils the saturant chemicals may gradually leach into the surrounding soil over time. This results in a gradual decrease in the corrosion protection.
In those instances where saturant leaching may occur, one way to prevent leaching is to use a multiple layer protective sheet having a plastic film membrane layer with a saturated felt layer on one side or a plastic film membrane between two layers of saturated felt. In use, the plastic membrane provides a cover for the felt and prevents leaching of the saturant chemicals. Furthermore, the plastic membrane also provides a permanent electrical barrier between the metal substructure and the contiguous soil. Existing protective materials of this type are made by first saturating the felt and then applying the plastic membrane to the felt. The membrane is held to the felt solely by the tackiness of the saturant chemicals in the felt. This does not securely hold the membrane on the felt, making installation of the protective material difficult, due to the easy separation of the felt and plastic.
The protective sheet material of the present invention also includes a felt layer and a plastic membrane. However, with the present sheet material, the felt and plastic membrane are heat fused together prior to the application of the saturant chemicals to the felt. As an alternative to heat fusion, an adhesive can be used to bond and hold the two layers together. Subsequent to the heat fusion or adhesive bonding of the layers, the felt is saturated with the petroleum wax, including corrosion inhibitors, plasticizers and/or bactericides. The result is a protective sheet material in which the plastic membrane and the felt cannot be easily separated from one another. The material is more durable and is thus easier to handle during the application process. The protective sheet material of the present invention is provided on rolls that can be several feet in width or as narrow as two or three inches.
The protective sheet material provides corrosion protection on the surface of underground structures. The protective sheet material also functions as a dielectric barrier to electrically insulate the underground structure.
In addition to covering underground pipelines, the sheet material of this invention can be used as a wrap for pilings, a waterproofing barrier beneath a highway pavement or on a foundation wall, and can be used as a landfill liner. Above ground applications include protecting a utility pole or the above ground portion of a piling, etc.
In one embodiment, the protective sheet material is formed with two layers, a plastic membrane layer and a felt layer.
In another embodiment, the protective sheet material is formed with a total of three layers, two layers of felt with the plastic membrane layer sandwiched between the felt layers. When this material is overlapped at a seam, a felt-to-felt seal is formed. However, the outer layer of the protective material will be saturated felt. This outer layer could be subjected to possible leaching of the saturant chemicals depending upon the soil type. This is not problematic, however, as the inner felt layer remains protected by the plastic to provide the desired corrosion protection.
While protective materials having a single layer of saturated felt and a layer of a plastic membrane with the two layers held together by the saturant chemicals are known in the art, a three layer protective material, having two layers of felt, is believed to be novel regardless of how it is manufactured.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.